Functional Expression of the Recombinant Spike Receptor Binding Domain of SARS-CoV-2 Omicron in the Periplasm of Escherichia coli.

A new severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variant known as Omicron has caused a rapid increase in recent global patients with coronavirus infectious disease 2019 (COVID-19). To overcome the COVID-19 Omicron variant, production of a recombinant spike receptor binding domain (RBD) is vital for developing a subunit vaccine or a neutralizing antibody. Although bacterial expression has many advantages in the production of recombinant proteins, the spike RBD expressed in a bacterial system experiences a folding problem related to disulfide bond formation. In this study, the soluble Omicron RBD was obtained by a disulfide isomerase-assisted periplasmic expression system in Escherichia coli. The Omicron RBD purified from E. coli was very well recognized by anti-SARS-CoV-2 antibodies, sotrovimab (S309), and CR3022, which were previously reported to bind to various SARS-CoV-2 variants. In addition, the kinetic parameters of the purified Omicron RBD upon binding to the human angiotensin-converting enzyme 2 (ACE2) were similar to those of the Omicron RBD produced in the mammalian expression system. These results suggest that an E. coli expression system would be suitable to produce functional and correctly folded spike RBDs of the next emerging SARS-CoV-2 variants quickly and inexpensively.

An analysis on clinical features and prognostic factors of gastrointestinal stromal tumors / 中华普通外科杂志

Objective To study the prognostic factors of gastrointestinal stromal tumors (GIST).Methods A total of 144 GIST patients treated at the First Affiliated Hospital of Guangxi Medical University between January 1996 and December 2011 were analyzed restrospectively.Kaplan-Meier,log-rank test and Cox regression model were used.Results The overall 5-year survival was 59.6％.Log-rank univariate survival analysis showed that the primary location,tumor size,metastasis,operational method,type of tumor cells,invasion of the surrounding organs and tissues,invasion of the smooth muscle,cellularity of the tumor,mitotic counts of the tumor cells,Ki-67 labeling index,P53 expression and targeting therapy were significant prognostic factors (P ＜ 0.05).Cox regression model showed that tumor size,metastasis,operational method,surrounding organs and tissues invasion,cellularity of the tumor,mitotic counts of the tumor cells,P53 and targeting therapy were essential to improve the survival.Conclusions The study suggests that early diagnosis and comprehensive treatment consisting of operation and targeting therapy can significantly improve the survival of GIST.